Tests: Fix flakey incentive e2e tests

[jasonpaulos]

Summary

Trying to make incentives tests less flakey.

Test Plan

Test change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.19%. Comparing base (82f4cde) to head (33f55b0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5986      +/-   ##
==========================================
+ Coverage   56.16%   56.19%   +0.02%     
==========================================
  Files         482      482              
  Lines       68027    68027              
==========================================
+ Hits        38209    38228      +19     
+ Misses      27224    27211      -13     
+ Partials     2594     2588       -6     

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[jannotti]

I'm happy with these. We might also try lengthening the round times a bit. I shrunk them all the way down to time.Second/2. Maybe 3/4 or a full second would prevent us from playing whack-a-mole on spurious errors.